1. Field of the Invention
The present invention relates to a cleaning and rinsing apparatus used in the manufacture of semiconductor devices (wafers).
2. Description of the Related Art
In the manufacture of wafers, particularly, highly-integrated semiconductor devices, a cleaning and rinsing operation is so essential that the manufacturing yield is dependent thereupon. For example, in a cleaning and rinsing operation, contamination, organic or inorganic particles, residual resist and ionic residue are removed from the surface of wafers without affecting the wafers.
In a first prior art cleaning and rinsing method, wafers are immersed in hot chemicals at a temperature of about 50.degree. C. to 90.degree. C. while ultrasonic waves are applied thereto. For example, an alkali solution such as an anmonia water/hydrogen peroxide water mixture (APM) is used to remove nonorganic particles, and an acid solution such as a hydrosulfurous acid/hydrogen peroxide water mixture (SPM) or hydrochloric acid/hydrogen peroxide water mixture (HPM) is used to remove organic particles and metal particles. Also, an alcohol solution such as an isopropyl alcohol solution (IPA) is used to remove organic particles. After a cleaning operation using such chemicals is completed, a rinsing operation using pure water is carried out. In this case, since such chemicals have a high viscosity, the rinsing operation is carried out at a relatively high temperature such as 90.degree. C. Particularly, since SPM includes 80 percent or more hydrosulfurous acid, the viscosity of SPM is very high.
In the first prior art cleaning and rinsing method, although contamination can be removed by chemicals, such chemicals, particularly, SPM cannot be flooded into fine-holes such as contact holes of the wafers, since such chemicals have high viscosity. As a result, it is impossible to completely remove contamination from the wafers.
Also, in the first prior art cleaning and rinsing method, even if use is made of hot pure water heated by a heater, groups of molecules of chemicals and pure water cannot be sufficiently separated. In addition, since the surface tension of the chemicals and the surface tension of pure water are both high, the wettabilities thereof on the wafers are low. As a result, such chemicals and pure water cannot be sufficiently flooded into highly-integrated holes of the wafers, and therefore, it is impossible to completely remove residual ions from the wafers.
In a second prior art cleaning and rinsing method, pure water is subjected to microwaves while the pure water comes into contact with a catalyst made of Pb or Pt particles. In this case, since the pure water is excited by the microwaves, groups of molecules of the pure water are separated into clusters, thus improving the wettability of the pure water. Then, wettability-improved pure water is moved to a use point where the contamination of wafers is removed by the pure water (see: JP-A-5-7869).
In the second prior art cleaning and rinsing method, however, the excited state of pure water cannot continue for a long time. For example, a duration time of the excited state is on the order of ms. Therefore, the pure water which has reached the use point loses activitity, and accordingly, the wafers may not be cleaned or rinsed.
Also, in the second prior art cleaning and rinsing method, since it is impossible to completely remove Pb or Pt particles as the catalyst by using state-of-the-art filtering technology, such particles may be adhered to the wafers, thus deteriorating the characteristics of the wafers.
Further, in the second prior art cleaning and rinsing method, although residual ions and a small amount of organic particles can be removed by the excited pure water, it is impossible to completely remove metal, nonorganic particles or particle contamination from the wafers due to the pure water's pH neutrality.